Interconnect structure and method for forming the same

ABSTRACT

An interconnection structure includes an interlevel insulating film, made of organic-containing silicon dioxide, between lower- and upper-level metal interconnects. A phenyl group, bonded to a silicon atom, is introduced into silicon dioxide in the organic-containing silicon dioxide.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to interconnection structure andmethod for forming the same in a semiconductor integrated circuit.

[0002] As the number of devices, integrated within a singlesemiconductor integrated circuit, has been tremendously increasing thesedays, wiring delay has also increasing noticeably. This is because thelarger the number of devices integrated, the larger line-to-linecapacitance (i.e., parasitic capacitance between metal interconnects),thus interfering with the performance improvement of a semiconductorintegrated circuit. The wiring delay is so-called “RC delay”, which isproportional to the product of the resistance of metal interconnectionand the line-to-line capacitance.

[0003] In other words, to reduce the wiring delay, either the resistanceof metal interconnection or the line-to-line capacitance should bereduced.

[0004] In order to reduce the interconnection resistance, IBM Corp.,Motorola, Inc., etc. have reported semiconductor integrated circuitsusing copper, not aluminum alloy, as a material for metal interconnects.A copper material has a specific resistance about two-thirds as high asthat of an aluminum alloy material. Accordingly, in accordance withsimple calculation, the wiring delay involved with the use of a coppermaterial for metal interconnects can be about two-thirds of thatinvolved with the use of an aluminum alloy material therefor. That is tosay, the operating speed can be increased by about 1.5 times.

[0005] However, the number of devices, integrated within a singlesemiconductor integrated circuit, will certainly continue to increase byleaps and bounds from now on, thus further increasing the wiring delayconsiderably. Therefore, it is concerned that even the use of copper asan alternate metal interconnection material would not be able to catchup with such drastic increase. Also, the specific resistance of copperas a metal interconnection material is just a little bit higher than,but almost equal to, that of gold or silver. Accordingly, even if goldor silver is used instead of copper as a metal interconnection material,the wiring delay can be reduced only slightly.

[0006] Under these circumstances, not only reducing interconnectionresistance but also suppressing line-to-line capacitance play a key rolein further increasing the number of devices that can be integratedwithin a single semiconductor integrated circuit. And the relativedielectric constant of an interlevel insulating film should be reducedto suppress the line-to-line capacitance. A silicon dioxide film hasheretofore been used as a typical material for an interlevel insulatingfilm. The relative dielectric constant of a silicon dioxide film is,however, about 4 to about 4.5. Thus, it would be difficult to apply asilicon dioxide film to a semiconductor integrated circuit incorporatingan even larger number of devices.

[0007] In order to solve such a problem, fluorine-doped silicon dioxidefilm, low-dielectric-constant spin-on-glass (SOG) film, organic polymerfilm and so on have been proposed as alternate interlevel insulatingfilms with respective relative dielectric constants smaller than that ofa silicon dioxide film.

[0008] The relative dielectric constant of a fluorine-doped silicondioxide film is about 3.3 to about 3.7, which is about 20 percent lowerthan that of a conventional silicon dioxide film. Nevertheless, afluorine-doped silicon dioxide film is highly hygroscopic, and easilyabsorbs water in the air, resulting in various problems in practice. Forexample, when the fluorine-doped silicon dioxide film absorbs water,SiOH groups, having a high relative dielectric constant, are introducedinto the film. As a result, the relative dielectric constant of thefluorine-doped silicon dioxide film adversely increases, or the SiOHgroups react with the water during a heat treatment to release H₂O gas.In addition, fluorine free radicals, contained in the fluorine-dopedsilicon dioxide film, segregate near the surface thereof during a heattreatment and react with Ti, contained in a TiN layer formed thereon asan adhesion layer, to form a TiF film, which easily peels off.

[0009] An HSQ (hydrogen silsesquioxane) film, composed of Si, O and Hatoms, is an exemplary low-dielectric-constant SOG film. In the HSQfilm, the number of the H atoms is about two-thirds of that of the Oatoms. However, the HSQ film releases a larger amount of water than aconventional silicon to dioxide film. Accordingly, since it is difficultto form buried interconnection in the HSQ film, a patterned metal filmshould be formed as metal interconnects on the HSQ film.

[0010] Also, since the HSQ film cannot adhere strongly to metalinterconnects, a CVD oxide film should be formed between the metalinterconnects and the HSO film to improve the adhesion therebetween.However, in such a case, if the CVD oxide film is formed on the metalinterconnects, then the substantial line-to-line capacitance is equal tothe serial capacitance formed by the HSQ and CVD films. This is becausethe CVD oxide film with a high dielectric constant exists between themetal interconnects. Accordingly, the resulting line-to-line capacitanceis larger as compared with using the HSQ film alone.

[0011] An organic polymer film, as well as the low-dielectric constantSOG film, cannot adhere strongly to metal interconects. Accordingly, aCVD oxide film should be formed as an adhesion layer between the metalinterconnects and the organic polymer film, too.

[0012] Moreover, an etch rate, at which an organic polymer film isetched, is approximately equal to an ash rate, at which a resist patternis ashed with oxygen plasma. Accordingly, a usual resist applicationprocess is not applicable in such a situation, because the organicpolymer film is likely to be damaged during ashing and removing theresist pattern. Therefore, a proposed alternate process includes:forming a CVD oxide film on an organic polymer film; forming a resistfilm on the CVD oxide film; and then etching the resist film using theCVD oxide film as an etch stopper, or a protective film.

[0013] However, during the step of forming the CVD oxide film on theorganic polymer film, the surface of the organic polymer film is exposedto a reactive gas containing oxygen. Accordingly, the organic polymerfilm reacts with oxygen to take in polar groups such as carbonyl groupsand ketone groups. As a result, the relative dielectric constant of theorganic polymer film disadvantageously increases.

[0014] Also, in forming inlaid copper interconnects in the organicpolymer film, a TiN adhesion layer, for example, should be formed aroundwiring grooves formed in the organic polymer film, because the organicpolymer film cannot adhere strongly to the metal interconnects. However,since the TiN film has a high resistance, the effective cross-sectionalarea of the metal interconnects decreases. Consequently, the intendedeffect attainable by the use of the copper lines, i.e., reduction inresistance, would be lost.

SUMMARY OF THE INVENTION

[0015] An object of the present invention is providing aninterconnection structure, in which an interlevel insulating film with alow dielectric constant can be formed to adhere strongly to organicfilm, oxide film or metal film, and a method for forming the same.

[0016] A first interconnection structure according to the presentinvention includes an interlevel insulating film, made oforganic-containing silicon dioxide, between lower- and upper-level metalinterconnects. In the organic-containing silicon dioxide, a phenylgroup, bonded to a silicon atom, is introduced into silicon dioxide.

[0017] In the first interconnection structure, a phenyl group, bonded toa silicon atom, is introduced into silicon dioxide in theorganic-containing silicon dioxide as a material for the interlevelinsulating film. Accordingly, such a film can be processed as well as aconventional CVD oxide film, has a relative dielectric constant as lowas that of an HSQ film, and can adhere strongly to organic film, oxidefilm or metal film. Thus, the number of devices that can be integratedwithin a single semiconductor integrated circuit can be easily increasedwithout modifying the conventional semiconductor device manufacturingprocess. As a result, a high-performance semiconductor integratedcircuit, operative at a high speed and with lower power dissipation, isrealized.

[0018] A second interconnection structure according to the presentinvention includes: lower-level metal interconnects; a first insulatingfilm formed over the lower-level metal interconnects and mainly composedof organic-containing silicon dioxide, in which silicon dioxide containsan organic component; a second insulating film formed over the firstinsulating film and mainly composed of an organic component; upper-levelmetal interconnects formed in the second insulating film; and contactsformed in the first insulating film to interconnect the lower- andupper-level metal interconnects.

[0019] In the second interconnection structure, a first insulating film,mainly composed of organic-containing silicon dioxide, is formed under asecond insulating film mainly composed of an organic component. Thus, informing wiring grooves by etching the second insulating film using aresist pattern as a mask, the first insulating film, mainly composed oforganic-containing silicon dioxide and having a low relative dielectricconstant, functions as an etch stopper. That is to say, since a CVDoxide film with a high dielectric constant need not be formed as an etchstopper under the second insulating film, the relative dielectricconstant of this interlevel insulating film can be lower than that of aconventional interlevel insulating film.

[0020] In one embodiment of the present invention, a phenyl group,bonded to a silicon atom, is preferably introduced into silicon dioxidein the organic-containing silicon dioxide.

[0021] In such an embodiment, the relative dielectric constant of thefirst insulating film can be further reduced and the adhesion betweenthe first insulating film and the lower-level metal interconnects can beimproved.

[0022] A third interconnection structure according to the presentinvention includes: metal interconnects; a first insulating film, whichis formed over the metal interconnects to cover the metal interconnectsand to leave grooves between the metal interconnects and is mainlycomposed of organic-containing silicon dioxide, in which silicon dioxidecontains an organic component; a second insulating film, which is formedon the first insulating film to fill in the grooves and has a relativedielectric constant lower than that of the first insulating film; and athird insulating film, which is formed over the second insulating filmand has a composition different from that of the second insulating film.

[0023] In the third interconnection structure, a first insulating film,mainly composed of organic-containing silicon dioxide adhering stronglyto metal interconnects, is interposed between the metal interconnectsand a second insulating film. Accordingly, there is no need to interposea high-dielectric-constant adhesion layer between the metalinterconnects and a second insulating film. Also, the first insulatingfilm is formed over the metal interconnects to leave groovestherebetween and the second insulating film, having a relativedielectric constant lower than that of the first insulating film, isformed to fill in the grooves. That is to say, the second insulatingfilm with a lower relative dielectric constant is interposed between themetal interconnects. As a result, the relative dielectric constant ofthe interlevel insulating film can be greatly lower than that of aconventional one.

[0024] In one embodiment of the present invention, the second insulatingfilm is preferably mainly composed of an organic component, and thethird insulating film is preferably mainly composed oforganic-containing silicon dioxide, in which silicon dioxide contains anorganic component.

[0025] In another embodiment of the present invention, a phenyl group,bonded to a silicon atom, is preferably introduced into silicon dioxidein the organic-containing silicon dioxide.

[0026] A first method for forming an interconnection structure accordingto the present invention includes the steps of: forming an interlevelinsulating film out of organic-containing silicon dioxide overlower-level metal interconnects by a CVD process using a reactive gascontaining phenyltrimethoxy silane, a phenyl group, bonded to a siliconatom, being introduced into silicon dioxide in the organic-containingsilicon dioxide; forming wiring grooves and contact holes, communicatingwith the wiring grooves and exposing the lower-level metalinterconnects, in the interlevel insulating film; and formingupper-level metal interconnects and contacts, interconnecting the lower-and upper-level metal interconnects together, by filling in the wiringgrooves and the contact holes with a metal film.

[0027] In the first method for forming an interconnection structure, anorganic-containing silicon dioxide film is formed by a CVD process usinga reactive gas containing phenyltrimethoxy silane. Thus, anorganic-containing silicon dioxide film, in which a phenyl group, bondedto a silicon atom, is introduced into silicon dioxide, can be formedwith certainty. Accordingly, an interlevel insulating film, which can beprocessed as well as a conventional CVD oxide film, has a relativedielectric constant as low as that of an HSQ film, and can adherestrongly to organic film, oxide film or metal film, can be formedbetween the lower- and upper-level metal interconnects with certainty.

[0028] A second method for forming an interconnection structureaccording to the present invention includes the steps of: forming afirst insulating film, mainly composed of organic-containing silicondioxide, in which silicon dioxide contains an organic component, overlower-level metal interconnects; forming a second insulating film,mainly composed of an organic component, over the first insulating film;forming wiring grooves and contact holes, which communicate with thewiring grooves and expose the lower-level metal interconnects, byselectively etching the second and first insulating films, respectively;and forming upper-level metal interconnects and contacts,interconnecting the lower- and upper-level metal interconnects together,by filling in the wiring grooves and the contact holes with a metalfilm.

[0029] In the second method for forming an interconnection structure, afirst insulating film, mainly composed of organic-containing silicondioxide, in which silicon dioxide contains an organic component, isformed over lower-level metal interconnects, and then a secondinsulating film, mainly composed of an organic component, is formed overthe first insulating film. Thus, in the step of forming wiring groovesby selectively etching the second insulating film, the first insulatingfilm functions as an etch stopper. That is to say, since a CVD oxidefilm with a high dielectric constant need not be formed as an etchstopper under the second insulating film, the relative dielectricconstant of this interlevel insulating film can be lower than that of aconventional one.

[0030] In one embodiment of the present invention, a phenyl group,bonded to a silicon atom, is preferably introduced into silicon dioxidein the organic-containing silicon dioxide.

[0031] In such an embodiment, the relative dielectric constant of thefirst insulating film can be further reduced and the adhesion betweenthe first insulating film and the lower-level metal interconnects can beimproved.

[0032] A third method for forming an interconnection structure accordingto the present invention includes the steps of: forming a firstinsulating film, mainly composed of organic-containing silicon dioxide,in which silicon dioxide contains an organic component, over metalinterconnects to cover the metal interconnects and to leave groovesbetween the metal interconnects; forming a second insulating film,having a relative dielectric constant lower than that of the firstinsulating film, on the first insulating film to fill in the grooves;and forming a third insulating film, having a composition different fromthat of the second insulating film, over the second insulating film.

[0033] In the third method for forming an interconnection structure, afirst insulating film, mainly composed of organic-containing silicondioxide, is formed over metal interconnects to leave groovestherebetween, and then a second insulating film, having a lower relativedielectric constant, is formed over the first insulating film to fill inthe grooves. Accordingly, there is no need to interpose ahigh-dielectric-constant adhesion layer between the metal lines and thesecond insulating film. Instead, the second insulating film with a lowrelative dielectric constant is interposed between the metalinterconnects. As a result, the relative dielectric constant of theinterlevel insulating film can be greatly lower than that of aconventional one.

[0034] In one embodiment of the present invention, the second insulatingfilm is preferably mainly composed of an organic component, and thethird insulating film is preferably mainly composed oforganic-containing silicon dioxide, in which silicon dioxide contains anorganic component.

[0035] In such an embodiment, a third insulating film, mainly composedof organic-containing silicon dioxide, is formed over a secondinsulating film mainly composed of an organic component. Accordingly, inthe step of ashing and removing a resist pattern with plasma, it ispossible to prevent the second insulating film from being damaged by theplasma.

[0036] In this case, a phenyl group, bonded to a silicon atom, ispreferably introduced into silicon dioxide in the organic-containingsilicon dioxide.

[0037] In such an embodiment, the relative dielectric constant of thethird insulating film can be further reduced and the adhesion betweenthe third insulating film and metal interconnects to be formed on thethird insulating film can be improved.

[0038] A fourth method for forming an interconnection structureaccording to the present invention includes the steps of: forming afirst insulating film over lower-level metal interconnects; forming asecond insulating film, which has a different composition than that ofthe first insulating film and is mainly composed of an organiccomponent, over the first insulating film; forming a conductive film onthe second insulating film; forming a first resist pattern, having aplurality of openings for forming wiring grooves, on the conductivefilm; etching the conductive film using the first resist pattern as amask, thereby forming a mask pattern out of the conductive film to havethe openings for forming wiring grooves; forming a second resistpattern, having a plurality of openings for forming contact holes, overthe first resist pattern; selectively etching the second insulatingfilm, thereby patterning the second insulating film to have the openingsfor forming contact holes and removing the first and second resistpatterns; etching the first insulating film using the patterned secondinsulating film as a mask, thereby forming contact holes in the firstinsulating film to expose the lower-level metal interconnects; etchingthe second insulating film using the mask pattern as a mask, therebyforming wiring grooves in the second insulating film; and filling in thewiring grooves and the contact holes with a metal film, thereby formingupper-level metal interconnects and contacts interconnecting the lower-and upper-level metal interconnects together.

[0039] In the fourth method for forming an interconnection structure,the composition of the first insulating film, in which the contact holesare formed, is different from that of the second insulating film inwhich the wiring grooves are formed. Accordingly, in forming the wiringgrooves by etching the second insulating film using a mask pattern as amask, the first insulating film functions as an etch stopper. As aresult, the depth of the wiring grooves can be self-aligned with thethickness of the second insulating film. Also, since the secondinsulating film is mainly composed of an organic component, the firstand second resist patterns are removed during the step of forming theopenings for forming contact holes in the second insulating film byselectively etching the second insulating film. That is to say, there isno need to perform the step of ashing and removing the first and secondresist patterns. As a result, it is possible to prevent the secondinsulating film, mainly composed of an organic component, from beingdamaged during an ashing process step.

[0040] In one embodiment of the present invention, the first insulatingfilm is preferably mainly composed of organic-containing silicondioxide, in which silicon dioxide contains an organic component.

[0041] In such an embodiment, there is no need to interpose ahigh-dielectric-constant adhesion layer between the metal interconnectsand the second insulating film. As a result, the relative dielectricconstant of the interlevel insulating film can be greatly lower thanthat of a conventional one.

[0042] In this case, a phenyl group, bonded to a silicon atom, ispreferably introduced into silicon dioxide in the organic-containingsilicon dioxide.

[0043] In such an embodiment, the relative dielectric constant of thefirst insulating film can be further reduced and the adhesion betweenthe metal interconnects and the first insulating film can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIGS. 1(a) through 1(c) are cross-sectional views illustratingrespective process steps for forming an interconnection structureaccording to the first embodiment of the present invention.

[0045] FIGS. 2(a) through 2(c) are cross-sectional views illustratingrespective process steps for forming the interconnection structure ofthe first embodiment.

[0046] FIGS. 3(a) through 3(c) are cross-sectional views illustratingrespective process steps for forming the interconnection structure ofthe first embodiment.

[0047] FIGS. 4(a) through 4(c) are cross-sectional views illustratingrespective process steps for forming an interconnection structureaccording to the second embodiment of the present invention.

[0048] FIGS. 5(a) through 5(c) are cross-sectional views illustratingrespective process steps for forming the interconnection structure ofthe second embodiment.

[0049] FIGS. 6(a) through 6(c) are cross-sectional views illustratingrespective process steps for forming the interconnection structure ofthe second embodiment.

[0050] FIGS. 7(a) through 7(c) are cross-sectional views illustratingproblems caused by the misalignment of the second resist pattern duringthe process of forming the interconnection structure of the secondembodiment

[0051] FIGS. 8(a) through 8(c) are cross-sectional views illustratingthe problems caused by the misalignment of the second resist patternduring the process of forming the interconnection structure of thesecond embodiment.

[0052] FIGS. 9(a) through 9(c) are cross-sectional views illustratingthe problems caused by the misalignment of the second resist patternduring the process of forming the interconnection structure of thesecond embodiment.

[0053] FIGS. 10(a) through 10(c) are cross-sectional views illustratingmeasures to solve the problems caused by the misalignment of the secondresist pattern during the process of forming the interconnectionstructure of the second embodiment.

[0054] FIGS. 11(a) through 11(c) are cross-sectional views illustratingthe measures to solve the problems caused by the misalignment of thesecond resist pattern during the process of forming the interconnectionstructure of the second embodiment.

[0055] FIGS. 12(a) through 12(c) are cross-sectional views illustratingrespective process steps for forming an inter-connection structureaccording to the third embodiment of the present invention.

[0056] FIGS. 13(a) through 13(c) are cross-sectional views illustratingrespective process steps for forming the interconnection structure ofthe third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] Embodiment 1

[0058] Hereinafter, interconnection structure and method for forming thesame according to the first embodiment of the present invention will bedescribed with reference to FIGS. 1(a) through 1(c), FIGS. 2(a) through2(c) and FIGS. 3(a) through 3(c).

[0059] First, as shown in FIG. 1(a), a first silicon nitride film 102 isformed over first metal interconnects 101 formed on a semiconductorsubstrate 100. The first silicon nitride film 102 is formed to be 50 nmthick, for example, and to protect the first metal interconnects 101during a subsequent etching process step. Thereafter, a firstorganic-containing silicon dioxide film 103, containing an organiccomponent in silicon dioxide, is formed to be 1 μm thick, for example,on the first silicon nitride film 102. Next, a second silicon nitridefilm 104 is formed to be 50 nm thick, for example, on the firstorganic-containing silicon dioxide film 103 and to protect the firstorganic-containing silicon dioxide film 103 during a subsequent etchingprocess step. Then, a second organic-containing silicon dioxide film105, containing an organic component in silicon dioxide, is formed to be400 nm thick, for example, on the second silicon nitride film 104. Thefirst and second organic-containing silicon dioxide films 103 and 105may be deposited by any arbitrary technique. For example, these films103 and 105 may be deposited by a CVD process using a reactive gasmainly composed of phenyltrimethoxy silane. In such a case, first andsecond organic-containing silicon dioxide films 103 and 105, in which aphenyl group, bonded to a silicon atom, is introduced into silicondioxide, can be obtained.

[0060] Next, as shown in FIG. 1(b), a first resist pattern 106, havingopenings for forming contact holes, is formed by lithography on thesecond organic-containing silicon dioxide film 105. Then, the firstorganic-containing silicon dioxide film 103, the second silicon nitridefilm 104 and the second organic-containing silicon dioxide film 105 aredry-etched using the first resist pattern 106 as a mask, thereby formingcontact holes 107 in the first organic-containing silicon dioxide film103 as shown in FIG. 1(c).

[0061] Subsequently, as shown in FIG. 2(a), a second resist pattern 108,having openings for forming wiring grooves, is formed by lithography onthe second organic-containing silicon dioxide film 105. Then, the secondorganic-containing silicon dioxide film 105 is dry-etched using thesecond resist pattern 108 as a mask, thereby forming wiring grooves 109,communicating with the contact holes 107, in the secondorganic-containing silicon dioxide film 105 as shown in FIG. 2(b). Inthis dry-etching process step, etching is performed under suchconditions that the second organic-containing silicon dioxide film 105is etched at a rate higher than the rate at which the second siliconnitride film 104 is etched.

[0062] Subsequently, the first silicon nitride film 102 is dry-etchedusing the first organic-containing silicon dioxide film 103 as a mask,thereby exposing the first metal interconnects 101 within the contactholes 107 as shown in FIG. 2(c).

[0063] Then, as shown in FIG. 3(a), the second resist pattern 108 isremoved. Subsequently, as shown in FIG. 3(b), a metal film 110 isdeposited over the entire surface of the substrate to completely fill inthe contact holes 107 and the wiring grooves 109. In this embodiment,the metal film 110 may be made of any arbitrary metal. For example,copper, aluminum, gold, silver, nickel, cobalt, tungsten, or an alloythereof may be used. Also, the metal film 110 may be deposited by anyarbitrary technique. For instance, plating, CVD or sputtering may beemployed.

[0064] Finally, as shown in FIG. 3(c), portions of the metal film 110,which are deposited on the second organic-containing silicon dioxidefilm 105, are removed by a CMP to technique, for example. As a result,second metal interconnects 111 and contacts 112, interconnecting thefirst and second metal interconnects 101 and 111, are formed out of themetal film 110.

[0065] In this embodiment, after the contact holes 107 have been formed,the wiring grooves 109 are formed. Alternatively, the contact holes 107and the wiring grooves 109 may be formed in the reversed order.

[0066] It should be noted that a multilevel interconnection structuremay be formed by forming respective films, interconnects and contacts onthe second metal interconnects 111 through the same process steps asthose described above.

[0067] In the first embodiment, the first and second organic-containingsilicon dioxide films 103 and 105 are films formed by a CVD processusing a reactive gas mainly composed of phenyltrimethoxy silane(hereinafter, such films will be referred to as “PTMS films”).Accordingly, in the PTMS films, a phenyl group (organic group), bondedto a silicon atom, has been introduced into silicon dioxide. Thus, aPTMS film shows a relative dielectric constant as low as 3.2 or less,heat resistance as high as 450° C. or more and very low hygroscopicity,and releases as small an amount of water as a conventional silicondioxide film. That is to say, a PTMS film can be processedsatisfactorily.

[0068] In addition, unlike a fluorine-doped CVD oxide film, a PTMS filmdoes not contain fluorine free radicals. Thus, increase in relativedielectric constant due to high hygroscopicity, contact failureresulting from a high content of water and degradation or peeling at theinterface with a metal film owing to locally high concentration offluorine during heat treatment can be all avoided.

[0069] Moreover, adhesion of the PTMS film to a metal film is superiorto that of a low-dielectric-constant SOG film or an organic polymer filmto the metal film and approximately equal to that of a conventional CVDoxide film.

[0070] Furthermore, the PTMS film has both an organic group and asiloxane skeleton, and therefore can adhere strongly to organic film,oxide film or metal film. A conventional interlevel insulating film,like an organic polymer film or low-dielectric-constant SOG film,requires an adhesion layer formed around buried interconnects, a linerlayer formed under metal interconnects made of a patterned metal film ora cover film formed on metal interconnects. In contrast, the PTMS filmneeds none of these. Accordingly, the PTMS film can be used as aninterlevel insulating film by itself.

[0071] As described above, in the PTMS film, a phenyl group (organicgroup), bonded to a silicon atom, has been introduced into an oxidefilm. Thus, a PTMS film can be processed as well as a conventional CVDoxide film, shows a relative dielectric constant as low as that of anHSQ film and can adhere strongly to organic film, oxide film or metalfilm. Therefore, if a PTMS film is used as an interlevel insulating filmfor an interconnection structure in a semiconductor integrated circuit,the number of devices integrated can be easily increased by leaps andbounds without modifying the conventional semiconductor devicemanufacturing process. As a result, a semiconductor integrated circuit,operative at a high speed and with lower power dissipation, is realized.

[0072] Embodiment 2

[0073] Next, interconnection structure and method for forming the sameaccording to the second embodiment of the present invention will bedescribed with reference to FIGS. 4(a) through 4(c), FIGS. 5(a) through5(c) and FIGS. 6(a) through 6(c).

[0074] First, as shown in FIG. 4(a), a silicon nitride film 202 isformed over first metal interconnects 201 formed on a semiconductorsubstrate 200. The silicon nitride film 202 is formed to be 50 nm thick,for example, and to protect the first metal interconnects 201 during asubsequent etching process step. Thereafter, an organic-containingsilicon dioxide film 203, containing an organic component in silicondioxide, is formed to be 1 μm thick, for example, on the silicon nitridefilm 202. The organic-containing silicon dioxide film 203 may bedeposited by any arbitrary technique. For example, the film 203 may bedeposited by a CVD process using a reactive gas mainly composed ofphenyltrimethoxy silane. In such a case, an organic-containing silicondioxide film 203, in which a phenyl group, bonded to a silicon atom, isintroduced into silicon dioxide, can be obtained.

[0075] Next, an organic film 204, mainly composed of an organiccomponent, is deposited to be 400 nm thick, for example, on theorganic-containing silicon dioxide film 203. The organic film 204 may beany arbitrary film. For example, the film 204 may be a hydrocarbon filmor a fluorine-containing hydrocarbon film formed by plasma CVD, coatingor thermal CVD. More specifically, the organic film 204 may be Teflonfilm, oxygen-containing Teflon film, polyimide fluoride film or polyarylether film. Thereafter, a titanium nitride film 205 is formed to be 50nm thick, for example, on the organic film 204.

[0076] Next, as shown in FIG. 4(b), a first resist pattern 206, havingopenings for forming wiring grooves, is formed by lithography on thetitanium nitride film 205. Then, the titanium nitride film 205 isdry-etched using the first resist pattern 206 as a mask, thereby forminga mask pattern 207 out of the titanium nitride film 205 as shown in FIG.4(c).

[0077] Subsequently, a second resist pattern 208, having openings forforming contact holes, is formed by lithography over the organic film204 without removing the first resist pattern 206. Then, the organicfilm 204 is dry-etched, thereby forming a patterned organic film 204Ahaving the openings for forming contact holes as shown in FIG. 5(a). Inthis case, since the organic film 204 and the first and second resistpatterns 206 and 208 are all mainly composed of organic components, theetch rate of the organic film 204 is substantially equal to the etchrate of the first and second resist patterns 206 and 208. Accordingly,when the organic film 204 is dry-etched, the first and second resistpatterns 206 and 208 are also removed simultaneously.

[0078] Then, the organic-containing silicon dioxide film 203 isdry-etched using the patterned organic film 204A as a mask, therebyforming a patterned organic-containing silicon dioxide film 203A havingcontact holes 209 as shown in FIG. 5(b). In this process step, byselecting such etching conditions that the etch rate of theorganic-containing silicon dioxide film 203 is higher than that of thepatterned organic film 204A, it is possible to prevent the patternedorganic film 204A from being erroneously etched.

[0079] Next, the patterned organic film 204A is dry-etched using themask pattern 207 as a mask, thereby forming wiring grooves 210 in thepatterned organic film 204A as shown in FIG. 5(c).

[0080] Subsequently, the silicon nitride film 202 is dry-etched usingthe patterned organic-containing silicon dioxide film film 203A as amask, thereby forming a patterned silicon nitride film 202A and exposingthe first metal interconnects 201 inside the contact holes 209 as shownin FIG. 6(a).

[0081] Then, as shown in FIG. 6(b), a metal film 211 is deposited overthe entire surface of the substrate to completely fill in the contactholes 209 and the wiring grooves 210. In this embodiment, the metal film211 may be made of any arbitrary metal. For example, copper, aluminum,gold, silver, nickel, cobalt, tungsten, or an alloy thereof may be used.Also, the metal film 211 may be deposited by any arbitrary technique.For instance, plating, CVD or sputtering may be employed.

[0082] Finally, as shown in FIG. 6(c), respective portions of the metalfilm 211 and the mask pattern 207, which are deposited on the patternedorganic film 204A, are removed by a CMP technique, for example. As aresult, second metal interconnects 212 and contacts 213, interconnectingthe first and second metal interconnects 201 and 212, are formed out ofthe metal film 211.

[0083] It should be noted that a multilevel interconnection structuremay be formed by forming respective films, interconnects and contacts onthe second metal interconnects 212 through the same process steps asthose described above.

[0084] In the second embodiment, the organic-containing silicon dioxidefilm 203 is a PTMS film formed by a CVD process using a reactive gasmainly composed of phenyltrimethoxy silane as in the first embodiment.Accordingly, in the PTMS film, a phenyl group (organic group), bonded toa silicon atom, has been introduced into silicon dioxide. Thus, the PTMSfilm can be processed as well as a conventional CVD oxide film, shows arelative dielectric constant as low as that of an HSQ film and canadhere strongly to organic film, oxide film or metal film.

[0085] In addition, the first and second resist patterns 206 and 208 canbe removed during the process step of dry-etching the organic film 204.Thus, it is no longer necessary to ash and remove the first and secondresist patterns 206 and 208 with oxygen plasma. That is to say, it ispossible to prevent the organic film 204 from being damaged during thestep of ashing and removing a resist pattern. Accordingly, although theorganic film 204 with a low relative dielectric constant is used as aninterlevel insulating film, an ordinary resist application process isapplicable to this embodiment.

[0086] Moreover, after the contact holes 209 have been formed in theorganic-containing silicon dioxide film 203 by dry-etching theorganic-containing silicon dioxide film 203 using the patterned organicfilm 204A as a mask, the wiring grooves 210 are formed in the patternedorganic film 204A by dry-etching the patterned organic film 204A usingthe mask pattern to 207 as a mask. Accordingly, an insulating film,where the contact holes 209 are formed, may have a different compositionthan that of an insulating film, where the wiring grooves 210 areformed. In addition, since the contact holes 209 and the wiring grooves210 are formed separately in distinct dry etching process steps, thedepth of the wiring grooves 210 can match with the thickness of theorganic film 204. That is to say, the depth of the wiring grooves 210can be defined by self-alignment.

[0087] Hereinafter, problems caused by the misalignment of the secondresist pattern 208 with the first resist pattern 206 and measured takento solve the problems will be described.

[0088] First, it will be described with reference to FIGS. 7(a) through7(c), FIGS. 8(a) through 8(c) and FIGS. 9(a) through 9(c) what problemsare caused if the second resist pattern 208 has misaligned.

[0089] As in the second embodiment, a silicon nitride film 202 is firstformed to be 50 nm thick, for example, over first metal interconnects201 formed on a semiconductor substrate 200 as shown in FIG. 7(a).Thereafter, an organic-containing silicon dioxide film 203, containingan organic component in silicon dioxide, is formed to be 1 μm thick, forexample, on the silicon nitride film 202.

[0090] Next, an organic film 204, mainly composed of an organiccomponent, is formed to be 400 nm thick, for example, on theorganic-containing silicon dioxide film 203. Then, a titanium nitridefilm 205 is formed to be 50 nm thick, for example, on the organic film204.

[0091] Then, as shown in FIG. 7(b), a first resist pattern 206, havingopenings for forming wiring grooves, is formed on the titanium nitridefilm 205. Thereafter, the titanium nitride film 205 is dry-etched usingthe first resist pattern 206 as a mask, thereby forming a mask pattern207 out of the titanium nitride film 205 as shown in FIG. 7(c).

[0092] Subsequently, a second resist pattern 208, having openings forforming contact holes, is formed over the organic film 204 withoutremoving the first resist pattern 206. As can be seen if FIGS. 8(a) and4(c) are compared with each other, the second resist pattern 208 hasmisaligned with the first resist pattern 206 in this case.

[0093] Then, the organic film 204 is dry-etched, thereby forming apatterned organic film 204A having the openings for forming contactholes as shown in FIG. 8(b). As in the second embodiment, since theorganic film 204 and the first and second resist patterns 206 and 208are all mainly composed of organic components, the first and secondresist patterns 206 and 208 are removed simultaneously with thedry-etching of the organic film 204.

[0094] Then, the organic-containing silicon dioxide film 203 isdry-etched using the patterned organic film 204A as a mask, to therebyforming a patterned organic-containing silicon dioxide film 203A havingcontact holes 209 as shown in FIG. 8(c). In this case, since the secondresist pattern 208 has misaligned with the first resist pattern 206, thediameter of the contact holes 209 is smaller than desired.

[0095] Next, the patterned organic film 204A is dry-etched using themask pattern 207 as a mask, thereby forming wiring grooves 210 in thepatterned organic film 204A as shown in FIG. 9(a). Then, the siliconnitride film 202 is dry-etched using the patterned organic-containingsilicon dioxide film 203A as a mask, thereby forming a patterned siliconnitride film 202A and exposing the first metal interconnects 201 withinthe contact holes 209 as shown in FIG. 9(b).

[0096] Then, a metal film is deposited over the entire surface of thesubstrate to completely fill in the contact holes 209 and the wiringgrooves 210. Thereafter, respective portions of the metal film and themask pattern 207, which are deposited on the patterned organic film204A, are removed by a CMP technique, for example. As a result, secondmetal interconnects 212 are certainly formed out of the metal film 211.However, since the diameter of the contact holes 209 is smaller thandesired, the contact holes 209 cannot be completely filled in with themetal film and the first and second metal interconnects 201 and 212cannot be interconnected to each other, resulting in a contact failure.

[0097] Next, it will be described with reference to FIGS. 10(a) through10(c) and FIGS. 11(a) through 11(c) what measures should be taken tosolve the problems caused by the misalignment of the second resistpattern 208.

[0098] First, a second resist pattern 208, having openings for formingcontact holes, are formed through the same process steps as thosedescribed with reference to FIGS. 7(a) through 7(c) and FIG. 8(a). Inthis case, the second resist pattern 208 has also misaligned with thefirst resist pattern 206 (see FIG. 8(a)).

[0099] Thus, as shown in FIG. 10(a), the first resist pattern 206 andthe mask pattern 207 are dry-etched using the second resist pattern 208as a mask. In this manner, portions of the first resist pattern 206, notoverlapping with the second resist pattern 208, are removed and eachopening of the mask pattern 207 is expanded to be equal to or largerthan each opening for forming a wiring groove or each opening forforming a contact hole. As a result, the pattern for the openings forforming contact holes in the second resist pattern 208 can betransferred to the first resist pattern 206 and the mask pattern 207.

[0100] Then, the organic film 204 is dry-etched, thereby forming apatterned organic film 204A having the openings for forming contactholes as shown in FIG. 10(b). In this case, since the organic film 204and the first and second resist patterns 206 and 208 are all mainlycomposed of organic components, the first and second resist patterns 206and 208 are removed simultaneously with the dry-etching of the organicfilm 204.

[0101] Then, the organic-containing silicon dioxide film 203 isdry-etched using the patterned organic film 204A as a mask, therebyforming a patterned organic-containing silicon dioxide film 203A havingthe contact holes 209 as shown in FIG. 10(c). In this case, the secondresist pattern 208 has misaligned with the first resist pattern 206.However, the pattern for the openings for forming contact holes in thesecond resist pattern 208 has been successfully transferred to the firstresist pattern 206 and the mask pattern 207. Thus, the diameter of thecontact holes 209 is a predetermined size.

[0102] Next, the patterned organic film 204A is dry-etched using themask pattern 207 as a mask, thereby forming wiring grooves 210 in thepatterned organic film 204A as shown in FIG. 11(a). Then, the siliconnitride film 202 is dry-etched using the patterned organic-containingsilicon dioxide film 203A as a mask, thereby forming a patterned siliconnitride film 202A and exposing the first metal interconnects 201 withinthe contact holes 209 as shown in FIG. 11(b).

[0103] Then, a metal film is deposited over the entire surface of thesubstrate to completely fill in the contact holes 209 and the wiringgrooves 210. And respective portions of the metal film and the maskpattern 207, which are deposited on the patterned organic film 204A, areremoved by a CMP technique, for example. As a result, second metalinterconnects 212 and contacts 213, interconnecting the first and secondmetal interconnects 201 and 212, are formed out of the metal film, asshown in FIG. 11(c).

[0104] Embodiment 3

[0105] Next, interconnection structure and method for forming the sameaccording to the third embodiment of the present invention will bedescribed with reference to FIGS. 12(a) through 12(c) and FIGS. 13(a)through 13(c).

[0106] First, a metal film is deposited on a semiconductor substrate 300and then selectively dry-etched and patterned, thereby forming firstmetal interconnects 301. Then, a first organic-containing silicondioxide film 302 (ire., an exemplary first insulating film), containingan organic component in silicon dioxide, is deposited to be 20 nm thick,for example, and to cover the first metal interconnects 301 such thatgrooves are left between the first metal interconnects 301. The firstorganic-containing silicon dioxide film 302 may be deposited by anyarbitrary technique. For example, the film 302 may be deposited by a CVDprocess using a reactive gas mainly composed of phenyltrimethoxy silane.

[0107] Next, a low-dielectric-constant insulating film 303 (i.e., anexemplary second insulating film) is deposited to be 600 nm thick, forexample, over the first organic-containing silicon dioxide film 302 andto fill in the grooves in the first organic-containing silicon dioxidefilm 302. The low-dielectric-constant insulating film 303 may be an SOGfilm, such as an HSQ film, mainly composed of silicon dioxide or anorganic film mainly composed of an organic component.

[0108] The first organic-containing silicon dioxide film 302 can adherestrongly to metal interconnects, SOG film or organic film. This isbecause the organic-containing silicon dioxide film 302 has both organicgroups and silicon-oxygen bonds (siloxane skeleton). That is to say, thesilicon-oxygen bonds increase the adhesion to an SOG film or metalinterconnects, and the organic groups increase the adhesion to anorganic film.

[0109] Subsequently, as shown in FIG. 12(b), a second organic-containingsilicon dioxide film 304 (i.e., an exemplary third insulating film) isdeposited to be 800 nm thick, for example, over thelow-dielectric-constant insulating film 303. The secondorganic-containing silicon dioxide film 304 may be deposited by anyarbitrary technique. For example, the film 304 may be deposited by a CVDprocess using a reactive gas mainly composed of phenyltrimethoxy silane.Alternatively, an ordinary silicon dioxide film or a fluorine-dopedoxide film, not the second organic-containing silicon dioxide film 304,may be deposited as the third insulating film over thelow-dielectric-constant insulating film 303.

[0110] Thereafter, as shown in FIG. 12(c), the second organic-containingsilicon dioxide film 304 is planarized by a CMP technique, for example.Then, as shown in FIG. 13(a), a resist pattern 305, having openings forforming contact holes, is formed by lithography on the secondorganic-containing silicon dioxide film 304. Subsequently, the secondorganic-containing silicon dioxide film 304, the low-dielectric-constantinsulating film 303 and the first organic-containing silicon dioxidefilm 302 are dry-etched using the resist pattern 305 as a mask, therebyforming contact holes 306 and exposing the first metal interconnects301.

[0111] Next, as shown in FIG. 13(b), the resist pattern 305 is removedwith post-glow oxygen plasma or water plasma or by anisotropic oxygenplasma reactive etching. Then, a metal film is deposited over the secondorganic-containing silicon dioxide film 304 to fill in the contact holes306. And respective portions of the metal film, which are exposed on thesecond organic-containing silicon dioxide film 304, are removed by a CMPtechnique, for example, thereby forming contacts 307 out of the metalfilm as shown in FIG. 13(c). In this embodiment, the metal film may bemade of any arbitrary metal. For example, copper, aluminum, gold,silver, nickel, cobalt, tungsten, or an alloy thereof may be used. Also,the metal film may be deposited by any arbitrary technique. Forinstance, plating, CVD or sputtering may be employed.

[0112] Although not shown, if second metal interconnects are formed onthe second organic-containing silicon dioxide film 304 through the sameprocess step for the first metal interconnects 301, then a multilevelinterconnection structure can be formed.

[0113] In the third embodiment, the second organic-containing silicondioxide film 304 has been deposited on the low-dielectric-constantinsulating film 303 and then planarized. Alternatively, after thelow-dielectric-constant insulating film 303 has been planarized, thesecond organic-containing silicon dioxide film 304 may be deposited onthe low-dielectric-constant insulating film 303. In such a case, theupper surface of the planarized low-dielectric-constant insulating film303 is preferably aligned with the upper surface of the first metalinterconnects 301 or the first organic-containing silicon dioxide film302.

[0114] Also, in the third embodiment, after the first organic-containingsilicon dioxide film 302 has been deposited to cover the first metalinterconnects 301, the low-dielectric-constant insulating film 303 isdeposited to fill in the grooves in the first organic-containing silicondioxide film 302. That is to say, the first organic-containing silicondioxide film 302, adhering strongly to metal interconnects, SOG film ororganic film and having a low relative dielectric constant (e.g., 3.2 orless), is interposed between the first metal interconnects 301 and thelow-dielectric-constant insulating film 303 such as SOG film like an HSQfilm or organic film not adhering strongly to metal interconnects.Accordingly, it is not necessary to interpose a high-dielectric-constantadhesion layer between the low-dielectric-constant insulating film 303and the first metal interconnects 301.

[0115] Moreover, since the resist pattern 305 is formed on the secondorganic-containing silicon dioxide film 304, the secondorganic-containing silicon dioxide film 304 is not damaged during ashingand removing the resist pattern 305. This is because the ash rate of theresist pattern 305 is different from the etch rate of the secondorganic-containing silicon dioxide film 304.

[0116] As described above, in the third embodiment, the firstorganic-containing silicon dioxide film 302, adhering more strongly tothe first metal interconnects 301 and showing a lower relativedielectric constant, is used as the first insulating film in directcontact with the first metal interconnects. The low-dielectric-constantinsulating film 303 is used as the second insulating film interposedbetween the first metal interconnects 301. And the secondorganic-containing silicon dioxide film 304, adhering more strongly tosecond metal interconnects (not shown) and showing a lower relativedielectric constant, is used as the third insulating film in directcontact with the second metal interconnects. As a result, a highlyreliable interconnection structure can be formed while reducingeffective capacitance between interconnections, suppressing increase incontact resistance and preventing peeling of the interlevel insulatingfilm from the metal interconnects.

What is claimed is:
 1. An interconnection structure comprising aninterlevel insulating film, made of organic-containing silicon dioxide,between lower- and upper-level metal interconnects, wherein a phenylgroup, bonded to a silicon atom, is introduced into silicon dioxide inthe organic-containing silicon dioxide.
 2. An interconnection structurecomprising: lower-level metal interconnects; a first insulating filmformed over the lower-level metal interconnects and mainly composed oforganic-containing silicon dioxide, in which silicon dioxide contains anorganic component; a second insulating film formed over the firstinsulating film and mainly composed of an organic component; upper-levelmetal interconnects formed in the second insulating film; and contactsformed in the first insulating film to inter-connect the lower-andupper-level metal interconnects.
 3. The interconnection structure ofclaim 2 , wherein a phenyl group, bonded to a silicon atom, isintroduced into silicon dioxide in the organic-containing silicondioxide.
 4. An interconnection structure comprising: metalinterconnects; a first insulating film, which is formed over the metalinterconnects to cover the metal interconnects and to leave groovesbetween the metal interconnects and is mainly composed oforganic-containing silicon dioxide, in which silicon dioxide contains anorganic component; a second insulating film, which is formed on thefirst insulating film to fill in the grooves and has a relativedi-electric constant lower than that of the first insulating film; and athird insulating film, which is formed over the second insulating filmand has a composition different from that of the second insulating film.5. The interconnection structure of claim 4 , wherein the secondinsulating film is mainly composed of an organic component, and whereinthe third insulating film is mainly composed of organic-containingsilicon dioxide, in which silicon dioxide contains an organic component.6. The interconnection structure of claim 5 , wherein a phenyl group,bonded to a silicon atom, is introduced into silicon dioxide in theorganic-containing silicon dioxide.